Market pros would love to believe yesterday’s big rally means the market is on the mend – but they don’t.

“If I saw seven consecutive days like this, maybe I could believe the bottom is behind us,” said Larry Kudlow, chairman of Kudlow & Co., an economic forecasting and money management firm. “Unfortunately, I think it was just a sucker’s rally.”

The Dow soared 346.86, or 4.57 percent, to 7,938.79 – its eighth-biggest one-day point gain ever and its biggest gain in six weeks.

The big move up added $325 billion to investors’ portfolios – a drop in the bucket of the more than $6.1 trillion they’ve lost since the market topped out two years ago.

The only reasonable explanation any Wall Street pro could give for the big rally is a growing belief that the Fed will have to cut rates at its next meeting.

That’s because the latest round of data confirms the U.S. economy is still very weak. Retail sales are soft, and manufacturing just fell back into recession. What’s more, construction spending fell for the fourth straight month in August.

“This is part of a whole range of data that suggests that there is an economic slowdown going into the fourth quarter,” said Bruce Steinberg, chief economist at Merrill Lynch. “We believe the Fed will look at this as another sign of weakness.”

The Fed’s Open Market Committee, which sets short-term interest rates, met last month but decided not to cut interest rates because of mixed economic signals. It is not scheduled to meet this month, but is likely to cut rates at its next meeting on Nov. 6.

Traders said some investors were bargain hunting.

“It is just a very oversold market in the short term,” said Arthur Hogan, chief market analyst at Jefferies & Co. “When we post a rally like this, no one wants to get in the way, because we have been selling stocks for three years. After one of these selloffs, everyone hopes and prays it is the bottom. So that is why we get these exaggerated moves. But the fundamental macroeconomic problems are still going to be there when we wake up.”

Some of yesterday’s buying could also be attributed to a practice called short covering, in which investors who sold shares expecting the market to keep dropping are forced to buy stock to cover their positions when the market advances.

Indeed, some stocks that posted big gains yesterday are those that have been hardest hit this year.

Microsoft, for example, rose $2.49 to $46.23 yesterday, but still has a year-to-date loss of more than 30 percent.